Thursday, 18 Oct, 2007 Science

Evolution of Animal Vision - New Facts Discovered


Having conducted deep study of evolutionary history, scientists at the University of California in Santa Barbara have found the origins of photo-sensitivity in animals.

The scientists concentrated their attention at Hydra, the aquatic animal that belongs to cnidarians and has inhabited Earth for hundreds of millions of years. The scientists became the first to study and analyze light-receptive genes called opsins in cnidarians that represent an ancient class of animals that also comprises jellyfish, corals, and sea anemones.

The scientists didn't discover these vision genes in earlier evolving animals such as sponges, so they are able to put a date on the animals' light sensitivity evolution. Now the scientists have at their disposal a time frame for the light sensitivity evolution in the animal. They are aware its predecessors existed approximately 600 million years ago.

According to senior author Todd H. Oakley, the university's assistant professor of biology, there are only a few cases where scientists have discovered and documented the very specific mutational events that have led to new features during evolution.

As Mr. Oakley mentioned, anti-evolutionists often argue that mutations, essential part of evolution, can only eliminate traits and do not result in the appearance of new features. The study conducted by the scientists proves that such claims are absolutely wrong. The results of the study show very clearly that specific mutational changes in a particular duplicated gene allowed the interaction of new genes with proteins in new ways. These different interactions are fundamental for the vision genetic machinery, different in various groups of animals.

Hydras are predators, so the scientists believe that the animals use light sensitivity for finding prey. Hydras use opsin proteins all over their bodies, but they are concentrated specifically in the mouth area, near the animal's tip. Hydras have neither eyes nor light-receptive organs, however, the animals have worked out the genetic pathways that allow them to sense light.

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